Undo 10.1: Faster Investigations, Faster Recordings, and Support for Codex

Undo Suite 10.1 is out now for C, C++, Go, and Rust. 10.0 was the biggest release in our history because it introduced Undo AI, and 10.1 is about making the whole thing quicker, leaner, and easier to fit into the way your team already works. 

If Undo is new to you: we record what a program actually did as it ran, and give that runtime context to your AI agent so it can carry out root-cause analysis on problems it could not otherwise solve. This article explains it further.

Here is what shipped.

What’s new in Undo AI?

Investigations start much faster. Before Undo AI can answer anything, it gathers information about the recorded program. That phase is considerably faster in 10.1 and uses less memory: for programs with a lot of debug information it can be up to ten times faster.

Codex is supported in UDB. The ai command in UDB is no longer limited to Claude Code. Codex is now supported as well. Where more than one agent is available, you choose which one to use the first time you run ai, and can change that choice later with config ai agent. This applies to the ai command, which drives an agent itself and so needs specific integration with each one. The undo mcp MCP server is not restricted in this way, and works with any agent that supports the Model Context Protocol.

Floating licenses free themselves up. The undo mcp server now releases its floating license after a period of inactivity, so another engineer can take it. The server itself keeps running, because an agent would otherwise decide it was broken, and takes a license again the next time the agent uses Undo AI. The timeout is the one already set in your license. Handy if you have more engineers than seats.

New guidance on teaching your agent about your system. Undo teaches your agent how to investigate a recording, but Undo doesn’t know about your build, your test environment, or your codebase. A new documentation page, Teaching your AI agent about your system, explains how to give an agent that missing context, and suggests prompts you can use to get the agent to write that guidance for itself.

What’s new in UDB?

Recording and replay are faster. The code that the Undo Engine generates on x86-64 has been improved and uses less memory. Programs with a large amount of code benefit most, and can be recorded and replayed up to 60% faster. Code generation and memory use on ARM64 have been improved in the same way. Programs that modify their own code as they run, such as those running on a Java virtual machine, are faster to record and replay too, and a number of individual system calls are cheaper to record than they were in 10.0.

If you are considering what recording costs you in wall-clock terms, our performance benchmarks show measured overhead across sqlite, gzip, and ffmpeg workloads.

Python 3.14. The Python interpreter shipped with UDB has moved from 3.10 to 3.14. Every piece of Python that UDB runs now uses it: scripts written against the Automation API, and anything loaded with source, udb --command, or udb --init-command.

There is more to UDB in 10.1 than the changes above, including a couple of features that are still marked experimental. Read the full release notes for more information.

What’s new in Undo Team and OEM Editions?

Both editions get the faster recording and replay described above, plus the following.

Annotations. A program can now add extra information to its own execution history while it is being recorded, making that history easier to navigate later. A unit test program might annotate the start of each test case with its name; a server might annotate the start of each request. Annotations are added through the functions in the libundoex library and queried in UDB with the info annotations and ugo annotation commands.

Two new ways to control live-record. --save-on signal:NAME saves a recording when the program receives the named signal, for example --save-on signal:SEGV, even if the program installs a handler for that signal. The recording is saved at the point the signal is delivered, so the signal handler does not appear in it. live-record --try-for limits a recording to a wall-clock duration, so that live-record --try-for 10s stops recording after ten seconds.

Plus…

10.1 adds support for Ubuntu 26.04 LTS and Red Hat Enterprise Linux / Rocky Linux 9.8 and 10.2. Ubuntu 25.10 and Red Hat Enterprise Linux / Rocky Linux 9.4 and 9.5 are no longer supported, and Amazon Linux 2 has moved to extended support.

A few legacy features have been removed: the deprecated success, failure, and signal aliases for the live-record --save-on option, replaced by exit-zero, exit-non-zero, and exit-signal; and the undodb_load_get_times function, deprecated back in 6.3, replaced by undodb_get_log_extent.

The full 10.1 release notes show the complete detail.

Undo 10.1 is available now for C, C++, Go, and Rust. AI features require a license that has them enabled, so if you are an existing customer and Undo AI tells you it is disabled, get in touch and we will sort out an upgrade.